1. Field of the Invention
This invention relates to an improvement in variable bore ram packers for a ram-type blowout preventer used in oil and gas drilling operations. The improved ram packer is designed to generate more mobility and uniform movement of the metal inserts that are molded into the ram packer before subjecting the ram packer rubber to full loading. This allows the packer to better seal on the contours of the drill pipe disposed within the bore of the blowout preventer.
Ram-type blowout preventers are part of a pressure control system used in oil and gas drilling operations to control unexpected well bore pressure spikes or “kicks” as they are commonly referred to in the industry. The blowout preventer has a body with a vertical bore and a pair of laterally disposed opposing bonnet assemblies. Each bonnet assembly includes a piston which is laterally moveable within the bonnet assembly by pressurized hydraulic fluid. Replaceable sealing elements called “packers” are mounted within rams attached to the ends of the pistons which extend into the blowout preventer bore. When these pistons are moved to a closed position, commonly referred to as “closing the blowout preventer” or “closing the rams”, the vertical bore of the blowout preventer is sealed and the kick is contained. These packers are available in a variety of configurations designed to seal the blowout preventer bore when the opposing rams and pistons are moved to their closed position.
One type of ram with packer has ends designed to seal around pipe of a specific size in the blowout preventer bore when the blowout preventer is closed. Other rams with packers are configured to seal around a range of pipe sizes. It is the type designed to seal around a range of pipe sizes, called variable bore ram packers to which the present invention is directed. The ram packers form a pressure tight seal during a kick until the well bore pressure can be controlled. The well bore pressure can reach several thousand pounds per square inch during a kick. Each ram packer has a semicircular opening in its front face to form a seal around 180° of the outer periphery of the pipe. When the rams are closed as described above, the opposing ram packers meet and seal the entire 360° periphery of the pipe. The novel variable bore ram packer of the present invention is designed to increase mobility and movement of the packer insert array to ensure the metal inserts smoothly and uniformly surround the pipe to be sealed against and eliminate large rubber extrusion gaps in the annulus between the metal insert's central column and the pipe being sealed against.
In an effort to minimize the tearing and loss of mass of the elastomeric sealing element, numerous modifications and additions to the ram packer and particularly the elastomeric sealing element in ram-type blowout preventers have been used. The variable bore ram packer of the current invention offers a substantial improvement by offering a variable bore ram packer with a smoother movement of the metal insert array during closing operations and minimization of rubber extrusion gaps between the metal inserts and the pipe being sealed against.
2. Description of Related Art
The use of metal inserts in a conical-type blowout preventer is disclosed in U.S. Pat. No. 2,846,178 to B. S. Minor.
U.S. Pat. No. 3,897,038 to R. K. Le Rouax shows a ram type blowout preventer using metal inserts as an anti-extrusion means.
The use of metal inserts in an annular blowout preventer to control the stress level in the elastomeric packer unit is shown in U.S. Pat. No. 3,917,293 to G. E. Lewis et al.
U.S. Pat. No. 4,099,699 to H. Allen shows the use of irising metal inserts in an annular blowout preventer.
Another example of metal inserts in a variable bore blowout preventer in disclosed in U.S. Pat. No. 4,229,012 to B. C. Williams, III.
U.S. Pat. No. 4,444,404 to G. C. Parks, Jr. shows an example of a variable bore ram packer with interlocking anti-extrusion metal inserts.
Another example of a variable bore ram packer with interlocking anti-extrusion metal inserts is disclosed in U.S. Pat. No. 4,458,876 to G. R. Schaeper et al.
U.S. Pat. No. 4,550,895 to D. U. Shaffer shows an early version of a variable bore ram packer. This apparatus utilizes a plurality of annular segments embedded in the elastomeric rubber to aid in effectuating a seal.
U.S. Pat. No. 6,367,804 B1 to G. D. Watts discloses variable bore ram packer utilizing a pillar insert with top and bottom plates that are rotatable with respect to one another to allow sealing on taper tool joint connections.